False-Positive Iodine-131 Uptake Due to Wasp Sting.

Area of Science:

• Nuclear Medicine
• Endocrinology
• Dermatology

Background:

• Papillary thyroid carcinoma requires lifelong monitoring using Iodine-131 (I-131) whole-body scans.
• Interpreting I-131 scans requires careful correlation with clinical findings to avoid misdiagnosis.

Purpose of the Study:

• To report a case where a benign skin condition mimicked metastatic thyroid cancer on I-131 imaging.
• To emphasize the importance of thorough clinical evaluation in the follow-up of thyroid cancer patients.

Main Methods:

• A patient with a history of papillary thyroid carcinoma underwent a standard I-131 whole-body follow-up scan.
• Clinical examination and patient history were obtained to investigate an unexpected finding on the scan.

Main Results:

• Focal I-131 uptake was observed in the right posterior neck, suspicious for metastatic disease.
• A concurrent finding of a scab in the same region, attributed to a recent wasp bite, was noted.
• Serum thyroglobulin levels were undetectable, arguing against recurrent thyroid cancer.

Conclusions:

• Benign skin lesions, such as those from insect bites, can cause focal I-131 uptake and mimic thyroid cancer recurrence.
• Clinical correlation, including a detailed patient history and physical examination, is crucial for accurate interpretation of I-131 whole-body scans.